To control precisely and investigate maneuverability of an underwater vehicle in a nuclear power pool this article presents a study on the mathematical model and the thrust characteristics of a ducted propeller under the quasi-cavitation effect by a numerical method. Firstly, a mathematical model of a ducted propeller including the quasi-cavitation effect term which is often ignored, is established based on the thrust performance under different quasi-cavitation distances and the revolution speed by CFD. Then the pressure field near the suction and pressure surface of blades are analyzed, which reveals that the thrust increases with a decrease of the quasi-cavitation distance. Finally, the thrust performances under different conditions are experimentally measured in an open-water pool, which can verify the reliability of the mathematical model below the error of 10%. The results demonstrates that the presented method can be used to evaluate the dynamic mechanism of a propeller, and hold a potential to improve the control strategy.
The unsteady motion behavior of oil/gas two-phase flow in a novel ventless bearing chamber has significant impacts on the lubrication and heat transfer efficiency of bearings due to the various advantages of lower pressure levels and weaker rotating airflow effects. In this paper, the unsteady motion behavior of oil/gas two-phase flow in a ventless aero-engine bearing chamber is investigated by three-dimensional numerical simulation through the volume of fluid (VOF) method, and the numerical method is verified using published experimental data. The flow characteristics of oil/gas two-phase in the secondary flow and three-dimensional flow are investigated. The results show the evolution of vortices and the transition of the driving mode in the unsteady motion of oil/gas two-phase flow, and a criterion for the shift of the driving mode at different rotor speeds is proposed. As the rotation speed increases, the variation trend of the velocity field and pressure field of oil/gas two-phase flow is consistent, and the accumulation region of oil becomes inconspicuous. The results indicate a reference for enhancing the performance of lubrication systems for aero-engines.
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